This invention relates to a transparent solar heat collector utilizing solar radiation to heat and illuminate the interior of a building structure. More particularly, the present invention relates to employing infrared absorptive glass to convert preferably at least 90% of incident infrared radiation within the spectrum of incident solar radiation on the glass into thermal energy.
The concept of providing a converter member to absorb heat from incident solar radiation is not new in the art. In U.S. Pat. No. 3,981,293, there is disclosed a solar heat collector wherein a cover plate is mounted in a spaced relation to a solar heat absorber having a surface defining an absorption coefficient for solar radiation that is either different or the same as the emissivity coefficient for infrared energy. A copper oxide coating on the absorber provides an absorptive coefficient that is greater than the emissive coefficient for infrared energy. The absorptive and emissive coefficients are the same for infrared energy on a black surface. The absorber undergoes heating by the absorption of solar radiation. Heat from the absorber is used to heat an absorbing medium, such as water, or a mixture of ethylene glycol and water.
In U.S. Pat. No. 3,981,294, assigned to the same assignee as this application, there is disclosed an all-glass composite building panel wherein a heat absorbing membrane is positioned within a passageway for a black liquid. The membrane is used to absorb heat and transmit the heat to the liquid moving through the passageway. The passageway is formed by an all-glass construction that additionally includes a vacuum cell of an all-glass construction overlying the face surface of the liquid passageway. While these known forms of solar collectors include the use of glass to form the collector structure, they nevertheless are not transparent to the visible light spectrum so as to enable use of such forms of solar collectors to illuminate as well as supplying heat to a building structure. In other words, from an architectural standpoint, opaque solar heat collectors are unusable as skylights and windows for a building structure. Moreover, transparent solar collectors offer greater architectural acceptance.
There are other solar heat collector designs wherein the circulating heat transfer fluid is air. The solar energy is absorbed by a metal structure coated with a selective absorption material. One form of such solar heat collector is based on the idea of a venetian blind-type collector wherein long narrow collector plates provide a large area for the absorption of solar energy. These strips are coated with a film of black paint to increase the heat absorbing property of the metal. The heat absorbing strips extend in a spaced-apart parallel relation between panels used to form a passageway for air to undergo heating by the strips.
The present invention is based on the discovery that commercially-available glasses transmit up to about 90% of the visible radiation within the spectrum of solar radiation. However, such glasses absorb nearly 100% infrared radiation. The present invention is, therefore, based on utilizing the unique heat absorbing properties of such glasses to form an absorber for infrared radiation within the spectrum of incident solar radiation for conversion into thermal energy.